320 



[. IKEDA : A NEW ASTOMATOUS CILIATE 



structures aboved described. It should further serve to illustrate an im- 

 portant structure not yet mentioned, 77,7., the micronuclcus. This is 

 a small, deeply staining- body which, in all the specimens examined, occur- 

 red in a single number, independently of and situated closely external 

 . to, the meganuclcar basketwork. It always lies 



in the transverse plane passing through the middle 

 of the body. It is of an ellipsoidal or spindle-like 

 shape, measuring about 5/2 in the major diamètre. 

 There can be distinguished in it a deeply stained 

 peripheral and a less deeply stained central part. 

 Around the body there always exists a narrow 

 clear space, which docs not seem to be an artificial 

 production, since it shows itself to be stained 

 though very lightly. There can scarcely be a 

 doubt that the above body represents the micro- 

 nucleus of the organism. 



The large central body differs from all the 

 cytoplasmic structures in being perfectly homo- 

 geneous and also in being but little stainable with 

 haematoxylin though very intensely with eosin. 

 This peculiarity indicates that it is not proto- 

 plasmic but is probably a colloid substance of a 

 protcidinous nature. It may be suggested that 

 the body in question is in all probability to 

 be looked upon as a sort of nutritive material in reserve, which is 

 contained in, and fills up, an excessively enlarged and centrally situated 

 vacuole. 



Together with the above apparently full-grown individuals were found 

 a number of much smaller — therefore assumably younger — specimens, which 

 showed some important structural peculiarities. To begin with the youn- 

 gest stage found, this was of an exceedingly small size in comparison mith 

 the full-grown individuals, measuring only about 20/2 by \Ofx (figs. 4 and 5). 



Fig- 3- 

 A small portion of a 

 section through M. sa- 

 gittae. Cytoplasmic layer 

 to the right ; central non- 

 plasmic body to the left. 

 M, a part of mega- 

 nucleus; m, micronuc- 

 leus. X960. 



